Due to their properties, phosphorescent transition metal complexes become more and more important as highly efficient emitters in optoelectronic components such as OLEDs. The spin-orbit coupling induced by the transition metal atom (heavy metal atom) results in an increased intersystem-crossing rate from the excited singlet state to the triplet state and thus in the use of the singlet excitons as well as the triplet excitions for emission and thereby allows a theoretical achievable internal quantum yield of 100%.
These phosphorescent dyes are usually introduced into appropriate energetically adjusted host materials. Polymeric structures are particularly suitable for this purpose due to the ease of processing by liquid processing from solution. Ideally, these should fulfill additional functions such as the spatial separation of the dye molecules to prevent undesirable concentration quenching processes and triplet-triplet-annihilation under emission reduction, increased charge carrier injection and transport and an increased recombination probability directly on the emitter molecules.
Thus, the combination of suitable polymeric host structures with appropriate statistically blended emitter compounds and additionally inserted charge transport molecules represents a method diversely used for the preparation of polymeric light emitting diodes (PLEDs). Even though the OLED components produced this way have mostly high efficiencies, these mixed systems can be subject to undesired phase separations, aggregations or crystallization processes, which have a negative effect on the capacity and the lifetime of the components. Therefore, the production of adapted (co)polymers, which fulfill additional functions such as charge transport and emission while at the same time using the advantages of liquid processing, is of steadily increasing interest.
For the synthesis of phosphorescent polymers with directly attached transition metal complexes the subsequent connection of the metal complexes to previously synthesized polymers provided with functional groups (“complexation to the polymer”) is known in the art. The optimizing such connection reactions is desirable.